Epidermal growth factor (EGF) is a low molecular weight (M.W. approximately 6000) polypeptide, isolated from mouse submaxillary glands and human urine, that stimulates the proliferation of cells in animals and in cell culture. This growth factor provides an excellent experimental approach to define in biochemical terms the mechanisms by which an extracellular molecule regulates cell growth. The main objectives of the research described in this proposal are 1) to define a subcellular biochemical system for studying the interaction of EGF with specific receptors and 2) to examine quantitatively and morphologically the activity and topology of EGF receptors in normal and tumor cells/tissue. A further goal is to obtain antibody to the EGF receptor and to determine the effect of the antibody in vivo and in cell culture systems. Since a detailed study of the biochemistry of EGF receptor interactions will require a defined preparation of the receptor and some understanding of physio-chemical properties of the receptor molecules, purification of the EGF receptor will be an initial objective. Term human placenta contains a higher level of EGF receptors than other tissues and will be used as source for the isolation of the EGF receptor. Concurrently with the isolation procedures, characterization of the binding of 125I-labeled EGF to membraneous and solubilized receptor preparations will be carried out. This will include kinetic analysis, specificity of EGF derivatives, and the influence of membrane active agents (e.g. phospholipase, lectins) and membrane components (e.g. phospholipids). The relationship of EGF receptor activity and distribution to abnormal cell growth will be explored using cultured cells and skin biopsies representative of normal, premalignant, and malignant skin tissues. Receptor activity will be determined by quantitating the binding of 125I-EGF to cells and tissues homogenates. Receptor distribution will be ascertained microscopically with fluorescein and ferritin conjugates of EGF, and with similar conjugates of antibody raised to the placental EGF receptor.